Solid electrolytic capacitor

ABSTRACT

A solid electrolytic capacitor comprises an insulating substrate in which an anode terminal and a cathode terminal are formed. The anode terminal comprises a first anode section formed on a first surface of the insulating substrate, and a second anode section formed on a second surface of the insulating substrate, which are electrically connected to each other. The cathode terminal comprises a first cathode section formed on the first surface and a second cathode section formed on the second surface, which are electrically connected to each other. A distance between the first anode section and the first cathode section is smaller than a distance between the second anode section and the second cathode section. And an anode section and a cathode section of a capacitor element are electrically connected to the first anode section and the first cathode section respectively.

This Application is a divisional of U.S. application Ser. No. 12/728,798filed Mar. 22, 2010, which the application Number 2009-069510, uponwhich this patent application is based, is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid electrolytic capacitor formedby mounting a capacitor element on an insulating substrate.

2. Description of Related Art

In a conventional solid electrolytic capacitor, as shown in FIG. 12, acapacitor element 101 is coated with an enclosure resin 102. Inside theenclosure resin 102, one end part 103 a of an anode terminal 103 isconnected to an anode section 101 a of the capacitor element 101, whileone end part 104 a of a cathode terminal 104 is connected to a cathodesection 101 b of the capacitor element 101. Both the anode terminal 103and the cathode terminal 104 are drawn out from the enclosure resin 102,and are bent along an outer peripheral surface of the enclosure resin102 so that the other end parts 103 b, 104 b of the terminals 103, 104are located along a lower surface 102 a of the enclosure resin 102. Theend parts 103 b, 104 b of both the terminals 103, 104 located along thelower surface 102 a of the enclosure resin 102 form lower surfaceelectrodes of the solid electrolytic capacitor.

In a manufacturing process of the solid electrolytic capacitor describedabove, required is a complicated step of bending the anode terminal 103and the cathode terminal 104. In addition, since the enclosure resin 102of appropriate thickness needs to be interposed between a lower surfaceof the capacitor element 101 and the lower surface electrodes, there hasbeen a problem of lower occupancy of the capacitor element 101 in thesolid electrolytic capacitor, or a problem of greater equivalent seriesresistance (ESR) or equivalent series inductance (ESL) due to anincrease in lengths of the anode terminal 103 and the cathode terminal104.

Therefore, as shown in FIG. 13, it has been proposed to form the solidelectrolytic capacitor by mounting the capacitor element 101 on aninsulating substrate 107 (e.g., a printed board) in which an anodeterminal 105 and a cathode terminal 106 are formed. In this solidelectrolytic capacitor, the anode terminal 105 comprises: a first anodesection 105 a formed on an upper surface 107 a of the insulatingsubstrate 107; a second anode section 105 b formed on a lower surface107 b of the insulating substrate 107; and an anode via 105 c opening inthe insulating substrate 107 to electrically connect the first anodesection 105 a and the second anode section 105 b to each other. Thecathode terminal 106 comprises: a first cathode section 106 a formed onthe upper surface 107 a of the insulating substrate 107; a secondcathode section 106 b formed on the lower surface 107 b of theinsulating substrate 107; and a cathode via 106 c opening in theinsulating substrate 107 to electrically connect the first cathodesection 106 a and the second cathode section 106 b to each other.

In the solid electrolytic capacitor described above, to the first anodesection 105 a, electrically connected is the anode section 101 a of thecapacitor element 101 through a pad member 108, while, to the firstcathode section 106 a, electrically connected is the cathode section 101b of the capacitor element 101 by a conductive adhesive. The secondanode section 105 b and the second cathode section 106 b form the lowersurface electrodes of the solid electrolytic capacitor.

Thus, by using the insulating substrate 107 to form the solidelectrolytic capacitor, a distance from the lower surface of thecapacitor element 101 to the lower surface electrodes decreases.Therefore, lengths of the anode terminal 105 and the cathode terminal106 decrease, resulting in reducing the ESR or ESL. Moreover, due to theemployment of the insulating substrate 107 in which the anode terminal105 and the cathode terminal 106 are formed, it is not necessary toexecute the complicated step of bending the anode terminal and thecathode terminal required in the manufacturing process of the solidelectrolytic capacitor shown in FIG. 12.

However, in the solid electrolytic capacitor shown in FIG. 13, since theanode section 101 a of the capacitor element 101 and the anode terminal105 are connected to each other by the pad member 108, required is acomplicated step of installing the pad member 108 on the anode terminal105 in the manufacturing process. In addition, the ESR or ESL mightincrease significantly due to poor connection or the like which occursbetween the pad member 108 and the anode terminal 105.

SUMMARY OF THE INVENTION

In view of above described problems, an object of the present inventionis to provide a solid electrolytic capacitor which iseasily-manufactured, and in which the ESR or ESL is reduced.

A first solid electrolytic capacitor according to the present inventioncomprises: a capacitor element including an anode section, a cathodesection, and a dielectric layer; and an insulating substrate in which ananode terminal and a cathode terminal are formed. The capacitor elementis mounted on the insulating substrate. Here, the anode terminalcomprises a first anode section formed on a first surface of theinsulating substrate on which the capacitor element is mounted, and asecond anode section formed on a second surface of the insulatingsubstrate located on an opposite side to the first surface, which areelectrically connected to each other. A connection part configured toelectrically connect the first anode section and the anode section ofthe capacitor element to each other is formed integrally with the firstanode section. The cathode terminal comprises a first cathode sectionformed on the first surface of the insulating substrate and a secondcathode section formed on the second surface of the insulatingsubstrate, which are electrically connected to each other. A distancebetween the first anode section and the first cathode section is smallerthan a distance between the second anode section and the second cathodesection. And the anode section and the cathode section of the capacitorelement are electrically connected to the connection part and the firstcathode section respectively.

According to the first solid electrolytic capacitor described above,since the connection part is formed integrally with the first anodesection of the anode terminal, it is not necessary to execute acomplicated step required in the manufacturing process of theconventional solid electrolytic capacitor in which the connection partand the first anode section are formed as separate members, namely acomplicated step of installing the connection part on the first anodesection before mounting the capacitor element on the insulatingsubstrate.

Further, in the solid electrolytic capacitor described above, theconnection condition between the connection part and the first anodesection is better than in the conventional solid electrolytic capacitorin which the connection part and the first anode section are formed asseparate members, and the ESR or ESL of the solid electrolytic capacitoris reduced.

Furthermore, in the solid electrolytic capacitor Desc1ribed above, sincethe distance between the first anode section and the first cathodesection is smaller than the distance between the second anode sectionand the second cathode section, the area of the first cathode sectioncan be increased. Therefore, the connection area between the firstcathode section and the cathode section of the capacitor element can beincreased, and as a result, the ESR or ESL of the solid electrolyticcapacitor is reduced.

A second solid electrolytic capacitor according to the present inventionis the first solid electrolytic capacitor described above, wherein onthe first surface of the insulating substrate, an anode section formingarea where the first anode section is formed and a cathode sectionforming area where the first cathode section is formed are included inthe same plane.

A third solid electrolytic capacitor according to the present inventionis the first or second solid electrolytic capacitor described above,wherein an end of the cathode section of the capacitor element and anend of the first cathode section of the cathode terminal which arelocated on the first anode section side are generally flush with eachother at a position spaced from the first anode section by apredetermined distance.

A fourth solid electrolytic capacitor according to the present inventionis any one of the first to third solid electrolytic capacitors describedabove, wherein the capacitor element includes an anode body from whichan anode lead is drawn out, the dielectric layer is formed on an outerperipheral surface of the anode body, a cathode layer is formed on anelectrolyte layer which is formed on the dielectric layer, the anodelead and the cathode layer form the anode section and the cathodesection of the capacitor element respectively, the connection partprojects on the first anode section, and the anode section of thecapacitor element is connected to an end of the connection part.

A fifth solid electrolytic capacitor according to the present inventionis any one of the first to third solid electrolytic capacitors describedabove, wherein the capacitor element includes a foil-like anode body,the dielectric layer is formed on a part of an outer peripheral surfaceof the anode body, a cathode layer is formed on an electrolyte layerwhich is formed on the dielectric layer, a part of the outer peripheralsurface of the anode body which is exposed from the dielectric layer andthe cathode layer form the anode section and the cathode section of thecapacitor element respectively, and the connection part is formed by apart of the outer peripheral surface of the first anode section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a solid electrolytic capacitoraccording to one embodiment of the present invention;

FIG. 2 is a cross-sectional view of a capacitor element included in thesolid electrolytic capacitor;

FIG. 3 a is a top view for explaining a first step of an electrodeforming step in a manufacturing process of the solid electrolyticcapacitor;

FIG. 3 b is a cross-sectional view for explaining the first step;

FIG. 4 a is a top view for explaining a second step of the electrodeforming step;

FIG. 4 b is a cross-sectional view for explaining the second step;

FIG. 5 a is a top view for explaining a third step of the electrodeforming step;

FIG. 5 b is a cross-sectional view for explaining the third step;

FIG. 6 a is a top view for explaining a fourth step of the electrodeforming step;

FIG. 6 b is a cross-sectional view for explaining the fourth step;

FIG. 7 a is a top view for explaining an element mounting step in themanufacturing process of the solid electrolytic capacitor;

FIG. 7 b is a cross-sectional view for explaining the element mountingstep;

FIG. 8 a is a top view for explaining a resin coating step and a cuttingstep in the manufacturing process of the solid electrolytic capacitor;

FIG. 8 b is a cross-sectional view for explaining the resin coating stepand the cutting step;

FIG. 9 is a cross-sectional view showing an example of modification ofthe solid electrolytic capacitor;

FIG. 10 is a cross-sectional view showing another example ofmodification of the solid electrolytic capacitor;

FIG. 11 is a cross-sectional view of a capacitor element included in thesolid electrolytic capacitor shown in FIG. 10;

FIG. 12 is a cross-sectional view showing a conventional solidelectrolytic capacitor; and

FIG. 13 is a cross-sectional view showing another conventional solidelectrolytic capacitor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention is described in detailbelow with reference to the drawings.

As shown in FIG. 1, a solid electrolytic capacitor according to theembodiment of the present invention is formed by mounting a capacitorelement 1 on an insulating substrate 5 and coating the capacitor element1 with an enclosure resin 2.

As shown in FIG. 2, the capacitor element 1 comprises an anode body 11from which an anode lead 12 is drawn out, a dielectric layer 13 formedon an outer peripheral surface of the anode body 11, an electrolytelayer 14 formed on the dielectric layer 13, and a cathode layer 15formed on the electrolyte layer 14.

The anode body 11 is formed by a porous sintered body made of a valvemetal. As the valve metal, used is, for example, tantalum, niobium,titanium, aluminum or the like.

The anode lead 12 comprises a part 121 which includes one end part 12 aand projects from the outer peripheral surface of the anode body 11, anda remaining part 122 buried in the anode body 11. The anode lead 12 isformed of a valve metal of the same kind as or different kind from thevalve metal forming the anode body 11, and the anode body 11 and theanode lead 12 are electrically connected to each other.

The dielectric layer 13 is formed by an oxide film formed on the outerperipheral surface of the anode body 11, and the oxide film is formed byimmersing the anode body 11 in an electrolytic solution such asphosphate aqueous solution, adipic acid aqueous solution or the like tooxidize the outer peripheral surface of the anode body 11electrochemically (anodic oxidation).

The electrolyte layer 14 is formed of an electrically-conductiveinorganic material such as manganese dioxide or the like, or anelectrically-conductive organic material such as TCNQ(Tetracyano-quinodimethane) complex salt, electrically-conductivepolymer or the like, and formed on the dielectric layer 13.

The cathode layer 15 is formed by a carbon layer formed on theelectrolyte layer 14 and a silver paste layer formed on the carbonlayer, and the electrolyte layer 14 and the cathode layer 15 areelectrically connected to each other.

In the capacitor element 1 described above, the part 121 of the anodelead 12 which is drawn out from the anode body 11 forms an anode sectionla of the capacitor element 1, while the cathode layer 15 forms acathode section lb of the capacitor element 1.

As shown in FIG. 1, the anode terminal 3 and the cathode terminal 4 areformed on the insulating substrate 5.

The anode terminal 3 comprises: a first anode section 31 formed on anupper surface 51 of the insulating substrate 5 on which the capacitorelement 1 is to be mounted; a second anode section 32 formed on a lowersurface 52 of the insulating substrate 5 located on an opposite side tothe upper surface 51; and an anode conductive layer 33 formed on a partof a side edge surface of the insulating substrate 5 to electricallyconnect the first anode section 31 and the second anode section 32 toeach other. The first anode section 31 is coated with the enclosureresin 2, while the second anode section 32 and the anode conductivelayer 33 are exposed from the enclosure resin 2.

A connection part 34 for electrically connecting the first anode section31 and the anode section la of the capacitor element 1 to each other isformed integrally with the first anode section 31. In this embodiment,the connection part 34 projects from an upper surface of the first anodesection 31. The anode section la of the capacitor element 1, namely theanode lead 12, is electrically connected to an end part of theconnection part 34 by welding.

Specifically, in the solid electrolytic capacitor according to thisembodiment, a first anode forming part 35 is formed on the upper surface51 of the insulating substrate 5, a second anode forming part 36 isformed on the lower surface 52 of the insulating substrate 5, and aconnection forming part 37 projects from an upper surface of the firstanode forming part 35. The connection forming part 37 is formedintegrally with the first anode forming part 35. A plating layer 38 isformed on: outer peripheral surfaces of the first anode forming part 35and the connection forming part 37 which are formed integrally with eachother; an outer peripheral surface of the second anode forming part 36;and a part of the side edge surface of the insulating substrate 5. Here,copper is used as a material of the first and second anode forming parts35, 36.

The first anode forming part 35 and a part of the plating layer 38 whichis formed on the outer peripheral surface of the first anode formingpart 35 form the first anode section 31 of the anode terminal 3. Thesecond anode forming part 36 and a part of the plating layer 38 which isformed on the outer peripheral surface of the second anode forming part36 form the second anode section 32 of the anode terminal 3. And, a partof the plating layer 38 which is formed on the side edge surface of theinsulating substrate 5 forms the anode conductive layer 33 of the anodeterminal 3.

Besides, the connection forming part 37 and a part of the plating layer38 which is formed on the outer peripheral surface of the connectionforming part 37 form the connection part 34.

The cathode terminal 4 comprises: a first cathode section 41 formed onthe upper surface 51 of the insulating substrate 5; a second cathodesection 42 formed on the lower surface 52 of the insulating substrate 5;and a cathode conductive layer 43 formed on a part of a side edgesurface of the insulating substrate 5 to electrically connect the firstcathode section 41 and the second cathode section 42 to each other. Thefirst cathode section 41 is coated with the enclosure resin 2, while thesecond cathode section 42 and the cathode conductive layer 43 areexposed from the enclosure resin 2. The cathode section 1 b of thecapacitor element 1, namely the cathode layer 15, is electricallyconnected to the first cathode section 41 by a conductive adhesive.

Specifically, in the solid electrolytic capacitor according to thisembodiment, a first cathode forming part 44 is formed on the uppersurface 51 of the insulating substrate 5, and a second cathode formingpart 45 is formed on the lower surface 52 of the insulating substrate 5.A plating layer 46 is formed on outer peripheral surfaces of the firstand second cathode forming parts 44, 45 and a part of the side edgesurface of the insulating substrate 5. Copper is used as a material ofthe first and second cathode forming parts 44, 45.

The first cathode forming part 44 and a part of the plating layer 46which is formed on the outer peripheral surface of the first cathodeforming part 44 form the first cathode section 41 of the cathodeterminal 4. The second cathode forming part 45 and a part of the platinglayer 46 which is formed on the outer peripheral surface of the secondcathode forming part 45 form the second cathode section 42 of thecathode terminal 4. And, a part of the plating layer 46 which is formedon the side edge surface of the insulating substrate 5 forms the cathodeconductive layer 43 of the cathode terminal 4.

The anode terminal 3 and the cathode terminal 4 are arranged on theupper surface 51 and the lower surface 52 of the insulating substrate 5so that a distance L1 between the first anode section 31 and the firstcathode section 41 is smaller than a distance L2 between the secondanode section 32 and the second cathode section 42.

The capacitor element 1 is arranged so that an end of the cathodesection lb of the capacitor element 1 and an end of the first cathodesection 41 of the cathode terminal 4 which are both located on the firstanode section 31 side are generally flush with each other at a positionspaced from the first anode section 31 by the predetermined distance L1.

The enclosure resin 2 coating the capacitor element 1 is formed on theupper surface 51 of the insulating substrate 5 so that the second anodesection 32 and the second cathode section 42 are exposed from theenclosure resin 2, and the anode conductive layer 33 and the cathodeconductive layer 43 are exposed from the enclosure resin 2. Therefore,in the solid electrolytic capacitor according to this embodiment, thesecond anode section 32 and the second cathode section 42 form the lowersurface electrodes, and, the anode conductive layer 33 and the cathodeconductive layer 43 are exposed from side surfaces of the enclosureresin 2.

In this embodiment, the upper surface 51 of the insulating substrate 5is flat and does not have a step. On the upper surface 51, an anodesection forming area 51 a where the first anode section 31 is formed anda cathode section forming area 51 b where the first cathode section 41is formed are included in the same plane.

A manufacturing method of the above described solid electrolyticcapacitor is explained below. In this manufacturing method, executed arean electrode forming step of forming the anode terminal 3 and thecathode terminal 4 on the insulating substrate 5, an element mountingstep of mounting the capacitor element 1 on the insulating substrate 5,a resin coating step of coating the capacitor element 1 with theenclosure resin 2, and a cutting step of cutting the insulatingsubstrate 5 to complete the solid electrolytic capacitor, in this order.

The electrode forming step includes first to fourth steps. In theelectrode forming step, the first to fourth steps are executed in thisorder.

In the first step, as shown in FIGS. 3 a and 3 b, one copper sheet 61 isbonded to an upper surface 531 of an insulating base 53 which is to bethe insulating substrate 5 of the solid electrolytic capacitor describedabove and one copper sheet 62 is bonded to a lower surface 532 of theinsulating base 53. As the copper sheet 61 to be bonded to the uppersurface 531 of the insulating base 53, employed is a sheet having agreater thickness than the copper sheet 62 to be bonded to the lowersurface 532.

In the second step, the copper sheet 62 bonded to the lower surface 532of the insulating base 53 is etched to form, as shown in FIG. 4 b, thesecond anode forming part 36 and the second cathode forming part 45which have generally the same thicknesses at positions spaced from eachother by a distance (L2+α) including the distance L2 and a distance acorresponding to thicknesses of the plating layers 38, 46 to bediscussed later.

Furthermore, the copper sheet 61 bonded to the upper surface 531 of theinsulating base 53 is etched to form, as shown in FIG. 4 b, the firstanode forming part 35 and the first cathode forming part 44 at positionsspaced from each other by a distance (L1+α) including the distance L1which is smaller than the distance L2 and the distance a correspondingto the thicknesses of the plating layers 38, 46 to be discussed later.The first anode forming part 35 has a smaller thickness than the coppersheet 61 and is provided with the connection forming part 37 projectingfrom the upper surface thereof. The first anode forming part 35 and thefirst cathode forming part 44 have generally the same thicknesses. Thus,by forming the first anode forming part 35 and the connection formingpart 37 from the one copper sheet 61, the first anode forming part 35and the connection forming part 37 are formed integrally with eachother.

In the third step, by punching out an area of the insulating base 53bounded by an Al line shown in FIG. 4 a, namely an area located on theopposite side of the first anode forming part 35 to the first cathodeforming part 44, formed is a through-hole 71 as shown in FIG. 5 a. Atthis time, end parts of the first and second anode forming parts 35, 36are punched out together with the area of the insulating base 53.Therefore, as shown in FIG. 5 b, side edge surfaces of the first andsecond anode forming parts 35, 36 are exposed to inside of thethrough-hole 71.

Further, by punching out an area of the insulating base 53 bounded by anA2 Line shown in FIG. 4 a, namely an area located on the opposite sideof the first cathode forming part 44 to the first anode forming part 35,formed is a through-hole 72 as shown in FIG. 5 a. At this time, endparts of the first and second cathode forming parts 44, 45 are punchedout together with the area of the insulating base 53. Therefore, asshown in FIG. 5 b, side edge surfaces of the first and second cathodeforming parts 44, 45 are exposed to inside of the through-hole 72.

By forming the through-hole 71 and the through-hole 72 as describedabove, the insulating substrate 5 on which the capacitor element 1should be mounted is formed by an area of the insulating base 53 betweenthe through-hole 71 and the through-hole 72.

In the fourth step, as shown in FIGS. 6 a and 6 b, plating is formed on:the outer peripheral surfaces of the first anode forming part 35 and theconnection forming part 37 which are formed integrally with each other;the outer peripheral surface of the second anode forming part 36; and apart of an inner surface of the through-hole 71, to form the platinglayer 38. Thus, the first anode forming part 35 and the second anodeforming part 36 are electrically connected to each other by the platinglayer 38, and the connection condition thereof is very good. Here,employed for the plating is a metal having high conductivity such ascopper, tin or the like.

Likewise, plating is formed on the outer peripheral surfaces of thefirst and second cathode forming parts 44, 45 and a part of an innersurface of the through-hole 72, to form the plating layer 46. Thus, thefirst cathode forming part 44 and the second cathode forming part 45 areelectrically connected to each other by the plating layer 46, and theconnection condition thereof is very good. Here, employed for theplating is a metal having high conductivity such as copper, tin or thelike.

By executing the first to fourth steps as described above, the firstanode forming part 35 and a part of the plating layer 38 which is formedon the outer peripheral surface of the first anode forming part 35 formthe first anode section 31 of the anode terminal 3, the second anodeforming part 36 and a part of the plating layer 38 which is formed onthe outer peripheral surface of the second anode forming part 36 formthe second anode section 32 of the anode terminal 3, and a part of theplating layer 38 which is formed on the inner surface of thethrough-hole 71 (namely the side edge surface of the insulatingsubstrate 5) forms the anode conductive layer 33 of the anode terminal3.

Besides, the connection forming part 37 and a part of the plating layer38 which is formed on the outer peripheral surface of the connectionforming part 37 form the connection part 34.

Further, the first cathode forming part 44 and a part of the platinglayer 46 which is formed on the outer peripheral surface of the firstcathode forming part 44 form the first cathode section 41 of the cathodeterminal 4, the second cathode forming part 45 and a part of the platinglayer 46 which is formed on the outer peripheral surface of the secondcathode forming part 45 form the second cathode section 42 of thecathode terminal 4, and a part of the plating layer 46 which is formedon the inner surface of the through-hole 72 (namely the side edgesurface of the insulating substrate 5) forms the cathode conductivelayer 43 of the cathode terminal 4.

Thus, on the insulating substrate 5, formed are the anode terminal 3comprising the first anode section 31 and the second anode section 32which are electrically connected to each other by the anode conductivelayer 33, and the cathode terminal 4 comprising the first cathodesection 41 and the second cathode section 42 which are electricallyconnected to each other by the cathode conductive layer 43. And, theconnection part 34 is formed integrally with the first anode section 31.

In the element mounting step, as shown in FIGS. 7 a and 7 b, thecapacitor element 1 is mounted on the upper surface 51 of the insulatingsubstrate 5, the anode section la of the capacitor element 1 iselectrically connected to the end part of the connection part 34 formedintegrally with the first anode section 31 by welding, and the cathodesection lb of the capacitor element 1 is electrically connected to thefirst cathode section 41 by the conductive adhesive. In the resincoating step, as shown in FIGS. 8 a and 8 b, the enclosure resin 2 isapplied to the upper surface 51 of the insulating substrate 5 to coatthe capacitor element 1 with the enclosure resin 2. At this time, thelower surface 52 of the insulating substrate 5, and the anode conductivelayer 33 and the cathode conductive layer 43 formed on the side edgesurface of the insulating substrate 5 are not coated with the enclosureresin 2 and maintained in an exposed state.

Therefore, the second anode section 32 and the second cathode section 42formed on the lower surface 52 of the insulating substrate 5 arearranged so as to be exposed from the enclosure resin 2, and, the secondanode section 32 and the second cathode section 42 form the lowersurface electrodes. And, the anode conductive layer 33 and the cathodeconductive layer 43 are exposed from the side surfaces of the enclosureresin 2.

In the cutting step, the insulating base 53 is cut along an A3-A3 lineand an A4-A4 line shown in FIG. 8 a. The solid electrolytic capacitorshown in FIG. 1 is thereby completed. This solid electrolytic capacitorhas a structure in which the connection part 34 is formed integrallywith the first anode section 31 of the anode terminal 3, and a structurein which the anode conductive layer 33 and the cathode conductive layer43 connected respectively to the second anode section 32 and the secondcathode section 42 which are to be the lower surface electrodes areexposed from the side surfaces of the enclosure resin 2.

Since a via is not formed in the insulating substrate 5 in the electrodeforming step in the solid electrolytic capacitor described above, it isnot necessary to execute in the manufacturing process a complicated steprequired in the manufacturing process of the conventional solidelectrolytic capacitor, namely a step of filling a via formed in theinsulating substrate 5 with a resin material in the manufacturingprocess of the conventional solid electrolytic capacitor. Therefore, thesolid electrolytic capacitor according to this embodiment can bemanufactured easily.

Furthermore, since the connection part 34 is formed integrally with thefirst anode section 31 of the anode terminal 3, it is not necessary toexecute a complicated step required in the manufacturing process of theconventional solid electrolytic capacitor in which the connection part34 and the first anode section 31 are formed as separate members (cf.FIG. 13), namely a complicated step of installing the connection part 34(pad member 108, FIG. 13) on the first anode section 31 before mountingthe capacitor element 1 on the insulating substrate 5.

In the case of mounting the solid electrolytic capacitor described aboveon a wiring board, the lower surface electrodes including the secondanode section 32 and the second cathode section 42 are soldered on aland on the wiring board.

As discussed above, the solid electrolytic capacitor described above hasa structure in which the anode conductive layer 33 and the cathodeconductive layer 43 connected respectively to the second anode section32 and the second cathode section 42 which are to be the lower surfaceelectrodes are exposed from the side surfaces of the enclosure resin 2.Therefore, solder wettability of the lower surface electrodes improves.In other words, when the lower surface electrodes are soldered on theland on the wiring board, a part of the solder can be easily providedaround side edge surfaces of the lower surface electrodes. Therefore, afillet is easily generated on the side edge surfaces of the lowersurface electrodes, and as a result, the connection condition betweenthe lower surface electrodes and the land on the wiring board is good.

As discussed above, since the solid electrolytic capacitor describedabove has a structure in which the connection part 34 is formedintegrally with the first anode section 31 of the anode terminal 3, theconnection condition between the connection part 34 and the first anodesection 31 is better than that in the conventional solid electrolyticcapacitor in which the connection part 34 and the first anode section 31are formed as separate members, and the ESR or ESL of the solidelectrolytic capacitor is reduced.

Further, in the solid electrolytic capacitor described above, thedistance L1 between the first anode section 31 and the first cathodesection 41 is smaller than the distance L2 between the second anodesection 32 and the second cathode section 42. Therefore, the area of thefirst cathode section 41 can be increased, and therefore, a connectionarea between the first cathode section 41 and the cathode section lb ofthe capacitor element 1 can be increased, and as a result, the ESR orESL of the solid electrolytic capacitor is reduced.

The inventors of the present application compared a solid electrolyticcapacitor shown in FIG. 1 and the conventional solid electrolyticcapacitor shown in FIG. 12 as to the ESR and ESL by using simulation.Both the solid electrolytic capacitors have the contour having a size of7.3 mm in length, 4.3 mm in width, and 1.8 mm in height, and the samecapacitor element was used for both capacitors. A measuring frequency ofthe ESL was 100 MHz.

The result showed that the ESR of the solid electrolytic capacitor shownin FIG. 1 was reduced around 17% compared to the ESR of the conventionalsolid electrolytic capacitor shown in FIG. 12. The result also showedthat the ESL of the solid electrolytic capacitor shown in FIG. 1 wasreduced around 25% compared to the ESL of the conventional solidelectrolytic capacitor shown in FIG. 12.

FIG. 9 is the cross-sectional view showing an example of modification ofthe solid electrolytic capacitor described above. As shown in FIG. 9,the plating layer 38 may be formed only on the outer peripheral surfaceof the first anode forming part 35, the outer peripheral surface of thesecond anode forming part 36, and the part of the side edge surface ofthe insulating substrate 5, without forming the plating layer 38 on theouter peripheral surface of the connection forming part 37. In the solidelectrolytic capacitor according to this modification, the connectionpart 34 is formed by the connection forming part 37 which is notprovided with the plating layer 38 on the outer peripheral surfacethereof.

Therefore, in the solid electrolytic capacitor according to themodification described above, the connection condition between theconnection part 34 and the anode section la by welding is not affectedby the formation condition of the plating layer 38.

FIG. 10 is a cross-sectional view showing another example ofmodification of the solid electrolytic capacitor described above. Asshown in FIG. 10, on the insulating substrate 5, a capacitor element 8including a foil-like anode body 81 may be mounted instead of thecapacitor element 1 described above.

Specifically, as shown in FIG. 11, the capacitor element 8 comprises theanode body 81, a dielectric layer 82 formed on a part of an outerperipheral surface of the anode body 81, an electrolyte layer 83 formedon the dielectric layer 82, and a cathode layer 84 formed on theelectrolyte layer 83.

For the anode body 81, used is a foil body made of a valve metal, on thesurface of which a porous layer is formed by etching. As the valvemetal, used is, for example, Aluminum, tantalum, niobium, titanium orthe like.

The dielectric layer 82 is formed by an oxide film formed on the part ofthe outer peripheral surface of the anode body 81, and the oxide film isformed by immersing a part of the anode body 81 in the electrolytesolution such as phosphate aqueous solution, adipic acid aqueoussolution or the like, to oxidize an outer peripheral surface of the partof the anode body 81 electrochemically (anodic oxidation).

The electrolyte layer 83 is formed of an electrically-conductiveinorganic material such as manganese dioxide or the like, anelectrically-conductive organic material such as TCNQ(Tetracyano-quinodimethane) complex salt, conductive polymer or thelike, and formed on the dielectric layer 82.

The cathode layer 84 is formed by a carbon layer formed on theelectrolyte layer 83 and a silver paste layer formed on the carbonlayer, and the electrolyte layer 83 and the cathode layer 84 areelectrically connected to each other.

In the capacitor element 8 described above, an exposed portion of theouter peripheral surface of the anode body 81 which is not covered bythe dielectric layer 82 forms an anode section 8 a of the capacitorelement 8, and the cathode layer 84 forms a cathode section 8 b of thecapacitor element 8.

In the solid electrolytic capacitor according to the modification, theanode section 8 a of the capacitor element 8 is electrically connectedto a partial area 31 a of the upper surface of the first anode section31 by welding. Therefore, the partial area 31 a of the upper surface ofthe first anode section 31 forms a connection part for electricallyconnecting the first anode section 31 and the anode section 8 a of thecapacitor element 8 to each other. The connection part is formedintegrally with the first anode section 31.

The cathode section 8 b of the capacitor element 8 is electricallyconnected to the first cathode section 41 by the conductive adhesive ina similar manner to the solid electrolytic capacitor shown in FIG. 1.

Also in the solid electrolytic capacitor according to the modificationdescribed above, it is not necessary to execute the complicated steprequired in the manufacturing process of the conventional solidelectrolytic capacitor in a similar manner to the solid electrolyticcapacitor shown in FIG. 1. Further, the solder wettability of the lowersurface electrodes improves better than in the conventional solidelectrolytic capacitor, and a fillet is easily generated on the sideedge surfaces of the lower surface electrodes, and as a result, theconnection condition between the lower surface electrodes and the landon the wiring board is good. Further, the ESR or ESL of the solidelectrolytic capacitor is reduced more than in the conventional solidelectrolytic capacitor.

Furthermore, also in the solid electrolytic capacitor according to themodification described above, since the distance L1 between the firstanode section 31 and the first cathode section 41 is smaller than thedistance L2 between the second anode section 32 and the second cathodesection 42 as shown in FIG. 10, the area of the first cathode section 41can be increased. Therefore, the connection area between the firstcathode section 41 and the cathode section 8 b of the capacitor element8 can be increased, and as a result, the ESR or ESL of the solidelectrolytic capacitor is reduced.

The present invention is not limited to the foregoing embodiment inconstruction but can be modified variously within the technical rangeset forth in the appended claims. In the embodiment described above,copper is used as the material of the first and second anode formingparts 35, 36 which form the anode terminal 3, and the material of thefirst and second cathode forming parts 44, 45 which form the cathodeterminal 4. However, this invention is not limited to this, and variouselectrically conductive materials can be used as said materials.

Further, the position and shape of the connection part 34 is not limitedto those shown in FIG. 1, and various positions and shapes of theconnection part 34 may be employed.

Furthermore, in the above described embodiment, the one copper sheet 62is etched to form the second anode forming part 36 forming the secondanode section 32 and the second cathode forming part 45 forming thesecond cathode section 42 in the second step (cf. FIG. 4 b), but thepresent invention is not limited to this. For example, it is alsopossible to prepare a copper sheet which is to be the second anodeforming part 36 and a copper sheet which is to be the second cathodeforming part 45 separately to bond them at the positions spaced fromeach other by the distance (L2+α).

The invention claimed is:
 1. A solid electrolytic capacitor comprising:a capacitor element including an anode section, a cathode section, and adielectric layer; and an insulating substrate in which an anode terminaland a cathode terminal are formed, the capacitor element being mountedon the insulating substrate, wherein the anode terminal comprises afirst anode section formed on a first surface of the insulatingsubstrate on which the capacitor element is mounted, and a second anodesection formed on a second surface of the insulating substrate locatedon an opposite side to the first surface, which are electricallyconnected to each other, wherein the cathode terminal comprises a firstcathode section formed on the first surface of the insulating substrateand a second cathode section formed on the second surface of theinsulating substrate, which are electrically connected to each other,wherein a distance between the first anode section and the first cathodesection is smaller than a distance between the second anode section andthe second cathode section, and the anode section and the cathodesection of the capacitor element are electrically connected to the firstanode section and the first cathode section respectively.
 2. The solidelectrolytic capacitor according to claim 1, wherein the first anodesection includes a first anode forming part formed on the first surfaceof the insulating substrate and a first anode plating layer formed on anouter peripheral surface of the first anode forming part, the secondanode section includes a second anode forming part formed on the secondsurface of the insulating substrate and a second anode plating layerformed on an outer peripheral surface of the second anode forming part,a third anode plating layer is formed on a part of a first side edgesurface of the insulating substrate, and the first to third anodeplating layers are integrally formed.
 3. The solid electrolyticcapacitor according to claim 2, wherein the capacitor element includesan anode body from which an anode lead is drawn out, a dielectric layerformed on an outer peripheral surface of the anode body, an electrolytelayer formed on the dielectric layer, and a cathode layer formed on theelectrolyte layer, the anode lead and the cathode layer form the anodesection and the cathode section of the capacitor element respectively,and the anode section of the capacitor element is connected to the firstanode plating layer.
 4. The solid electrolytic capacitor according toclaim 2, wherein the capacitor element includes a foil-like anode body,a dielectric layer formed on a part of an outer peripheral surface ofthe anode body, an electrolyte layer formed on the dielectric layer, acathode layer formed on the electrolyte layer, a part of the outerperipheral surface of the anode body which is exposed from thedielectric layer forms the anode section of the capacitor element, thecathode layer forms the cathode section of the capacitor element, andthe anode section of the capacitor element is connected to the firstanode plating layer.
 5. The solid electrolytic capacitor according toclaim 1, wherein an end of the cathode section of the capacitor elementand an end of the first cathode section of the cathode terminal whichare located on the first anode section side are generally flush witheach other at a position spaced from the first anode section by apredetermined distance.
 6. The solid electrolytic capacitor according toclaim 1, wherein the first cathode section includes a first cathodeforming part formed on the first surface of the insulating substrate anda first cathode plating layer formed on an outer peripheral surface ofthe first cathode forming part, the second cathode section includes asecond cathode forming part formed on the second surface of theinsulating substrate and a second cathode plating layer formed on anouter peripheral surface of the second cathode forming part, a thirdcathode plating layer is formed on a part of a second side edge surfaceof the insulating substrate, and the first to third cathode platinglayers are integrally formed.
 7. The solid electrolytic capacitoraccording to claim 6, wherein an outer peripheral surface of the cathodesection of the capacitor element has a first outer surface facing thefirst surface of the insulating substrate, the first outer surface isentirely provided above the first cathode plating layer.